Revista de la Facultad de Medicina (Apr 2000)
Cálculo de los contenidos arterial y venoso de oxígeno, de la diferencia arteriovenosa de oxígeno, tasa de extracción tisular de oxígeno y shunt intrapulmonar con unas nuevas fórmulas, basadas en la saturación de oxígeno
Abstract
Arterial blood gases sampling is a very useful tool in the evaluation of the peripheral perfusion state in the critically ill. Although extensively used, there is a high possibility of doing a wrong process of data, because the complexity of the mathematical formulations. In an attempt to simplify the operations devoted to evaluate the tissue perfusíon of patients in the intensive care unit, we propose a new group of formulations eliminating the free oxygen content in blood in the estimation of: arterial - venous oxygen difference (Dav02); oxygen extraction rate (Tex 02); oxygen blood content (co02) and intrapulmonary shunt (QS/QT). First, we compare retrospectively the results obtained using the traditional formulations and the new ones in a group of 100 samples selected by means of "random number" function of Excel ®. Then, we perform a prospective follow-up in two intensive ca re units in Santafé de Bogotá comparing the two methods of blood gases evaluation. Furthermore, we made the calculations using the arterial blood oxygen saturation given by the blood gases determination and the one obtained directly by the pulse- oxymeter, ussuaIy located at the index finger of the patient By using media comparison as well as linear regression analysis we could establish a high correlation index between the two methods of evaluation. These results demonstrate that it is possible to eliminate the free plasma oxygen content to perform an accurate evaluation of the peripheral perfusión state of the critically ill. Furthermore, by using the blood oxygen saturation obtained with a pulse-oxymeter, it could be possible even to avoid the procedure of blood gases sampling in sorne clinical settings.
